In general, electricity of a photovoltaic (PV) module is produced through a process of generating photocurrents by each solar cell unit, enhancing voltages by module concatenation, and converting the enhanced voltages to mains electricity. During the process, a condition such as breakdown, internal connection failure, stain, or obstruction occurring in any solar cell unit, or a destructive defect such as crack or air bubble occurring during module production, packaging, or delivering would cause current mismatch between solar cell units and induce a hot spot effect due to overheat. As long as any hot spot is formed on a solar cell unit, there is not only no benefit on overall electricity production, but the electricity produced by other solar cell units would also be consumed. The entire module would thereby undergo thermal breakdown or even cause fire hazards.
A hot spot endurance test on a PV module is conventionally based on defect recognition on electroluminescence (EL) images or thermal images. The recognition process may be affected due to sensor pixel size and weather limitations, and the inspection process may normally take several days to complete.